Recently, various assay devices that employ liquid crystals have been disclosed. For example, a liquid crystal assay device using mixed self-assembled monolayers (SAMs) containing octanethiol and biotin supported on an anisotropic gold film obliquely deposited on glass has been reported. Gupta, V. K.; Skaife, J. J.; Dubrovsky, T. B., Abbott N. L. Science, 279, (1998), pp. 2077-2079. In addition, PCT publication WO 99/63329 published on Dec. 9, 1999, discloses assay devices using SAMs attached to a substrate and a liquid crystal layer that is anchored by the SAM. U.S. Pat. No. 6,288,392 issued to Abbott et al. discloses the quantitative characterization of obliquely-deposited substrates of gold using atomic force microscopy and describes the influence of substrate topography on the anchoring of liquid crystals. U.S. Pat. No. 6,284,197 issued to Abbott et al. discloses the optical amplification of molecular interactions using liquid crystals. As disclosed by U.S. Pat. No. 6,284,197, interactions between molecules that are components of self-assembled monolayers and other molecules can be amplified and transduced into an optical signal through the use of a mesogenic layer. A device for detecting analytes is disclosed which includes a substrate onto which a self-assembled monolayer is attached and a mesogenic layer which is anchored by the self-assembled monolayer. The mesogenic layer undergoes a change in conformation in response to the molecular interaction.
Various other assay devices that employ liquid crystals have been disclosed. For example, U.S. Ser. No. 09/784,679 published on May 9, 2002, as U.S. Patent Publication No. U.S. 2002/0055093, discloses a rubbed substrate structure for use in a liquid crystal assay device. The rubbed substrate structure includes a biochemical blocking compound and a biomolecule recognition agent. The surface of the side of the support containing the biochemical blocking layer is rubbed such that it possesses features that drive the uniform anchoring of liquid crystals when the liquid crystals contact the side of the support containing the biochemical blocking layer. U.S. Ser. No. 09/784,232 published on Mar. 7, 2002, as U.S. Patent Publication No. U.S. 2002/0028451, discloses a method and apparatus for detection of microscopic pathogens. The detection apparatus includes a substrate with a detection region on a surface thereof, the detection region having microstructures including grooves formed therein that will align liquid crystal material in contact therewith. The detection apparatus also includes a blocking layer on the surface of the detection region of the substrate that does not disrupt the alignment of liquid crystal material in contact therewith. The blocking layer blocks nonspecific adsorption of pathogens to the surface, but a binding agent on the surface of the detection region of the substrate specifically binds to a selected pathogen.
As noted above, various liquid crystal assay devices have been reported that employ self-assembled monolayers formed on metallized surfaces. A need remains, however, for surfaces that possess gradients in surface topography and a method for forming and using such surfaces. A need also remains for a method of optimizing sensitivity and performance in liquid crystal assay devices that utilizes self-assembled monolayers formed on metallized surfaces.